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Doc.No. : EUM/OPS/DOC/06/1799
Issue : v3
Date : 5 July 2007
EUMETSATAm Kavalleriesand 31, D-64295 Darmstadt, Germany
Tel: +49 6151 807-7Fax: +49 6151 807 555 Telex: 419 320 metsat d
http://www.eumetsat.int
GEONETCast Global Design Document
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Document Signature Table
Removed for Internet Publication
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Document Change Record
Issue /Revision
Date DCN.No
Changed Pages / Paragraphs
V1 (draft) 21/09/2006 First release
V1a 26/09/06 Formal release internal to EUMETSAT
V2 (draft) 08/12/06 - Inclusion of FENGYUNCast
- new assessment on multicast systems
V3 05/07/07 Inclusion of comments from NOAA and WMO
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Table of Contents
1 GEONETCast Global Design.......................................................................................................71.1 Introduction..........................................................................................................................7 1.2 The Global Design...............................................................................................................9
2 The GEONETCAST OPERATIONS IMPLEMENTATION GROUP............................................113 DATA EXCHANGE DESIGN DISCUSSION...............................................................................12
3.1 Multicast: Stand-alone GNC systems are disseminating data via multicast listen-in (Turn-around-daisy-chaining) ................................................................................................................133.2 Private Network: N-N Inter-connected GNC systems .......................................................143.3 Scope of Dissemination.....................................................................................................143.4 Comparison Matrix of Data Exchange Options .................................................................14
4 DISTRIBUTED GEONETCAST PORTAL...................................................................................164.1 Data Discovery (online and offline) ...................................................................................16
4.1.1 Standardised Meta Data description for dissemination products .........................164.2 User Management .............................................................................................................17
5 MINIMUM REQUIREMENTS FOR A GEONETCAST GNC .......................................................186 CONCLUSION.............................................................................................................................187 INPUT TO GEONETCAST IMPLEMENTATION PLAN..............................................................19
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1 GEONETCAST GLOBAL DESIGN
This document presents a first version of the GEONETCast global design, the comprising
entities, responsibilities, functions and services. The document takes into consideration the
existing EUMETCast system by EUMETSAT and the NOAA visioning document on an
American GEONETCast component and the publications available on FENGYUNCast from
the Chinese Meteorological Administration (CMA).
1.1 IntroductionThe key base areas in the global GEONETCast design (Figure 4 and 5) are:
- The regional Multicast implementation (Figure 1 and 4)- The data exchange between the GEONETCast Regional Network Centres -
GNC(chapter 3)
- The data discovery and user management functionalities via a distributed portal(chapter 4)
At time of writing the GEONETCast system is technically based on EUMETCast.
Figure 1 Current EUMETCast System Overview
The current coverage of EUMETCast dissemination is shown in figure 2 followed by a
possibility of achieving a nearly global coverage by inclusion of the Asia4 (figure 3) footprint
as a turn-around satellite for the purpose of GEONETCast.
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Figure 2 Current EUMETCast coverage
Figure 3 Dataflow including the local American turn-around
AsiaS
Figure 3 GEONETCast Evolution
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1.2 The Global DesignThe conceptual idea of a global GEONETCast implementation is that several regional centres
take on the responsibilities for establishing a satellite based regional dissemination system -based on the EUMETCast general framework (Figure 1) and provide the same services to
the common user community. The concept of interconnected regional GEONETCast
Network Centres (GNC) would allow such an implementation.
Figure 4 GEONETCast Regional Network Centre - GNC
Each GNC would comprise the same components of 1) Data acquisition, 2) Service
management, 3) Uplink provider, 4) Turn around providers and 5) User community (figure 4
above) and additionally 5) cooperates with the partner GNCs over communication links.
Figure 5 High level design of GEONETCast implementation via interconnected GNC
Each GNC has the same functionality, services and obligations and is based on the same
technical framework (Figure 1 and 4). The GNC caters for the needs of the users in its
regional responsibility and exchanges those with the other centres to reach a global visibility
Satellite 1
Uplink Provider
GNC Service Management- users- data policy- infrastructure- Ops ImplementationGroup Member- Portal
GNCas DataProvider
ExternalData
Provider 1
ExternalData
Provider n
Communicationlines
TurnaroundProvider 1
Users
Users
Users
TurnaroundProvider N
Satellite 2
Satellite N
w
Other GNCs
User access to portal
GEONETCast NetworkCentre
Communication
lines for dataexchange
between GNCs
- GTS and itscomponents- RegionalNetwork- Internet- IP-VPN
- Leased Line
GEONETCast NetworkCentre
GEONETCast NetworkCentre
- GTS and itscomponents- RegionalNetwork- Internet- IP-VPN- Leased Line
- GTS and itscomponents- RegionalNetwork- Internet- IP-VPN
- Leased Line
DataProvider(s)
DataProvider(s)
DataProvider(s)
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2 THE GEONETCAST OPERATIONS IMPLEMENTATION GROUPThe GEONETCast Operations Implementation Group builds up on the existing structures to
decide on the high level topics of GEONETCast.
Structure
Composition
Roles
Processes
Services
The final setup for this group is TBC.
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3 DATA EXCHANGE DESIGN DISCUSSIONOne of the essential parts of the global GEONETCast design is the architecture of theinteroperability of the GNCs, in particular the data exchange for global and local
dissemination and the administrational data such as user and data policy information and the
Meta data description of the products to be disseminated (figure 6).
Figure 6 High level concept of GNC data exchange
User- Reception
System based on
regional standard
for GNC n
Delivers Local
Data to User via
regional
implementation
of GEONETCast
GEONETCast Regional Centre(GNC) 1
(incl. all Figure 1 components)
/provider1/local1/usergroup1
/providerN/localN/usergroupN
/provider1/GNC1/usergroup1
/providern/GNC1/usergroupn
/provider1/goencn/usergroup1
/providern/GNCn/usergroupn
LOCAL Service
Directories on uplink
GNC 1 Service
Directories on uplink
GNC n Service
Directories on uplink
GEONETCast Regional Centre(GNC) n
(incl. all Figure 1 components)
/provider1/local1/usergroup1
/providern/localn/usergroupn
/provider1/GNC1/usergroup1
/providern/GNC1/usergroupn
/provider1/goencn/usergroup1
/providern/GNC/usergroupn
LOCAL Service
Directories on uplink
GNC 1 Service
Directories on uplink
GNC n Service
Directories on uplink
Delivers Local
Data to User via
regional
implementation
of GEONETCast
Exchange of
Global Data Sets
Delivers Global
Data to User via
regional
implementation
of GEONETCast
User- Reception
System based on
regional standard
for GNC 1
- User DataBase (info,data policy)
- MetaData Repository
- User DataBase (info,data policy)
- MetaData Repository
Exchange of
administrational
data
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The overall purpose of the GNC dissemination exchange is to achieve the actual
dissemination of data for a global audience and regional audience at the same time. This is acore element in the overall GEONETCast design allowing the essential GNC interoperability.
Based on the above design concept (figure 6) two potential options have been identified to
date, which are discussed in the following sections.
3.1 Multicast: Stand-alone GNC systems are disseminating data via multicastlisten-in (Turn-around-daisy-chaining)
This concept is based on the assumption that all data that is included into the global
GEONETCast service is made available for dissemination to each GNC by the usage of
overlapping footprints in a turn-around daisy chain.
The current first version proof-of-concept prototype is such a system (figure 7). All data that
is to be disseminated into a region is recorded from a local receiving ground station which
forwards the data to the local dissemination satellite.
Figure 7 Multicast daisy-chains
This system assumes the availability of all hops at all times. If one hop should be unavailable
the entire chain is broken. In order to avoid this Single Point of Failure (SPF) a second loop
would be needed on which data flows into the other direction. This is considered very costly.
Furthermore this system assumes the availability of convenient overlapping footprints. Such
convenient footprints would have a beam into the area where the partner GNC uplink station
is to avoid additional terrestrial forwarding costs.
Such a system would only cater for the mission dissemination data but not for the exchange
of administrative data such as the web portal related traffic for which still a traditional
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network would be needed. The reliability of Turn-around-daisy-chaining depends on the
availability for all hops at all times and the availability of convenient overlapping satellite
footprints. It also does not easily permit the distribution of limited subsets of a given regionsbroadcast data stream to another regional GEONETCast Network Center (GNC).
3.2 Private Network: N-N Inter-connected GNC systems
The concept is based on the assumption that each GNC is connected in a bi-directional setup
to each other GNC (figure 8). For the current version of GEONETCast this would involve
around 3-4 centres. The very first implementation however is currently EUMETSAT and
NOAA (which already have those high bandwidth networks between each other) and
EUMETSAT and CMA (which is using Internet for data exchange).
Figure 8 Traditional N-N networks
This private network would cater for the exchange of all data for global dissemination, the
user data and any other administrative data including the exchange of product describingMeta data for the distributed GEONETCast portal.
3.3 Scope of Dissemination
It needs to be noted that not all data of all regions needs to be disseminated in all regions.
This sub-setting of products being pushed between regional GNCs is necessary to alleviate
the need for all GNCs to acquire enough transponder bandwidth to carry all regional products
from all GNCs across the globe. For each region, therefore, the operator of the GNC decides
what products are to be broadcast in that region.
3.4 Comparison Matrix of Data Exchange Options
GEONETCast
Regional Centre
(GNC) 1
(includes all Figure
4 components)
GEONETCast
Regional Centre
(GNC) 2
(includes all Figure
4 components)
GEONETCast
Regional Centre
(GNC) 3
(includes all Figure
4 components)
GEONETCast
Regional Centre
(GNC) n
(includes all Figure
4 components)
Traditional network (secure
Internet or Leased Line)
providing high redundant
bandwidth
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The matrix below (table 1) is a first qualitative assessment of the two options for data
exchange which would need to be reviewed after a detailed market, cost and effort survey and
analysis.
Table 1 Comparison between data exchange methods
Element Multicast Daisy Chain N-N Network
Support to high data rates yes yes
Data flow bi-directional no yes
Scalability high high
Interoperability to existing
infrastructure
high high
Admin effort high medium
Single Point of Failure yes noCost low * - high medium
Implementation effort low * - high low
Pre-requisites Availability of overlapping
footprints across the globe
no
Terrestrial line connection May be required Yes
Allows selection of specific
products for exchange
No (if packet based) Yes (if
file based)
Yes
* If overlaps are already existing as part of the regional mission
Conclusion: Depending upon the footprint coverage and existing network and dissemination
infrastructure both options can be considered as complementary to each other and
could exist in parallel.
The implementation effort of a N-N network is clearly smaller, easier to upgrade andrequires no special pre-requisites
Bi-directional traffic is an advantage for the N-N network because it reduces a singlepoint of failure in case one GNC is not available and caters to the dissemination of
(ad-hoc) user data as well as the routine dissemination contents
Both solutions are valid options and they comprise complementary implementation solutions.
The ideal path to exchange data is if each GNC can listen in to the multicast of the other
GNCs and then re-broadcasts this traffic on the regional GNC footprint.
An example of this implementation would be the listen-in of the Chinese EUMETCast
reception system in Kashi to EUMETCast transmissions. Kashi then forwards the data to
GNC Bejing via land line. GNC Bejing then re-transmitts this traffic via FENGYUNCast
over the entire Asian footprint.
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4 DISTRIBUTED GEONETCAST PORTAL
Each User accesses in the first instance a central GEONETCast portal on
http://www.geonetcast.org (one stop shop).
Based on the input of geographical information, the user is then re-directed to the responsible
regional GNC which hosts the regional implementation of the portal.
There the user can access services for:
Data discovery (searchable) on global and regional products and services;
Links to the regional service performance indicator and news messages;
Links to the help-desk services;
Links to the GEONETCast subscription service; Web links to the regional archives of the various data providers
Implementations of such distributed portals are widely available. It is pre-mature to discuss
now the actual portal technology to be used for GEONETCast; the only important aspect for
now is the requirement that the portal technology and implementation of its services should
follow recognised international standards.
4.1 Data Discovery (online and offline)
The data and service discovery is an essential service to the user which will allow access to
the Meta-data information on all disseminated products-, type-, contents-, format- and usage-
descriptions of each product and service in conjunction with small static sample data sets.
Essentially there are two implementations of this data discovery:
Online implementation. This requires Internet access of the user to the distributedGEONETCast Portal which hosts all of above services
Offline implementation. This is the static version of the data discovery service (alldescriptions, pages, samples etc.) which is disseminated via GEONETCast. It allows
each user access to and browse capability for the essential information about
GEONETCast products and services on the local reception station without the
necessity of Internet connectivity.
4.1.1 Standardised Meta Data description for dissemination products
All data types (not the instances) which are disseminated on GEONETCast (regional and
global) should be described with standardised Meta data information. The current standards
are the series of ISO 19100 standards and WMO Core Metadata Profile of the ISO Metadata
Standard. The WMO standard is currently implementing the related ISO standard. This will
allow the unified description of all data to be disseminated be it of meteorological,
oceanographic or other environmental nature.
Each data provider is responsible for the provision of the Meta data description of its owndata.
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The Meta data repository will be replicated and synchronized across all GNC. This
distributed option allows better scalability, redundancy and an overall better service to the
user.
In a further step the repository is being disseminated on GEONETCast on a dedicated global
news/information channel. This allows each user access and browse to the essential
information about GEONETCast products and services on the local reception station without
the necessity of Internet connectivity.
4.2 User ManagementEach regional GNC maintains their local user services and keeps records of the related user
information. The exchange of user information is not directly necessary unless a data policy
shall be applied to a user such as data denial. It is recommended to keep the amount of
exchanged user information to a minimum, limited to the users in a geographical location
with overlapping footprints or the ones to which a data policy shall be applied on instruction
of the responsible data provider or regional GNC.
The local user services contain as a minimum:
A call-desk
Information knowledge base on GEONETCast (HW, SW, configuration etc.)
User registration services
Provision of access to related technical documentation
Provision of a problem call handling system
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5 MINIMUM REQUIREMENTS FOR A GEONETCAST GNCTable 3 contains the high level requirements (HI-[number]) each organisation must fulfil inorder to join GEONETCast as a regional GNC.
Table 3 Minimum Requirements for a GEONETCast GNC
High Level Requirement Description
HI-010 Capability to endorse Data Policy on
individual level
HI-020 Capability of Denial-Of-Service
HI-030 Provision of a Management Layer
participating in the GNC Operations
Implementation Group including the
agreement to a trust relationship.
HI-040 Ability to manage and disseminate data
which goes beyond the standard
responsibilities of a regional organisation in
order to serve a global audience.
HI-050 Implementation of a regional GNC service as
specified in the GNC description and the
common service Service Level Agreement
(SLA)
HI-060 Implementation of User servicesHI-070 Implementation of the regional part of the
shared GEONETCast portal
HI-080 Capability to exchange selected global
dissemination products in data exchange
between the partner GNC
HI-090 Provide sufficient IT-security to assure data
integrity
HI-100 Provide a mechanism for adapting data
content to user requirements
HI-110 Provide specifications for widely available
user receiving devicesHI-120 Provide coverage of a substantial geographic
region such as at least a continent
6 CONCLUSION
The presented design allows GEONETCast implementation on the basis of proven
technologies and expertise, modern concepts of inter-organisational cooperation, and high
user friendliness and user services for relatively low implementation and operation costs.
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7 INPUT TO GEONETCAST IMPLEMENTATION PLAN
In order to progress with GEONETCast technical implementation, several steps are necessaryfor overall GEONETCast coordination. The highlevel items are described in the
GEONETCast Implementation Plan.
Agreement on the overall high level global design
Gathering and consolidation of high level user requirements (regional and global)which are addressing administrative services and also technical preferences.
Description of all regional services (administrative and data/product services)
Agreement on the data exchange technology
Agreement on a project plan for the implementation of an operational prototype inaccordance with an agreed SLA
Implementation of regional GNC including procurement of the related infrastructure
Implementation of global services e.g. the distributed GEONETCast portal but also ofGNC- Implementation Group services (user registration, data denial concepts, overall
cooperation agreements)
Preparation of an operational prototype installation of all regional functions of a GNCincluding the high-level GNC- Implementation Group functions
Presentation of the operational prototype to the user community and administrations
Agreement of an Interface Control Document (ICD) on How to join GEONETCastas a GNC, describing the pre-requisites each GNC must fulfil before they can join
the interconnected GNC with the required SLA and standards.
Above tasks are only outlining some high-level activities and will require detailed project
planning and the availability of the necessary cooperation agreements, funds and resources.
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